--- title: "Indoor propagation models (any two)" subject: "Wireless Communication" chapter: 3 key: "semester_7/wireless_communication:indoor-propagation-models" source: https://www.bctengineer.com/q/semester_7/wireless_communication/indoor-propagation-models site: BCT Engineering --- # Indoor propagation models (any two) Wireless Communication · Chapter 3: Radio Wave Propagation in Mobile Networks - Asked in: 2070 Bhadra, 8 marks - Video: [Indoor Propagation Model - Mobile Radio Propagation - Mobile Communication System](https://www.youtube.com/watch?v=6ze2mhZe31Q) — Ekeeda - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/wireless_communication/indoor-propagation-models - Whole chapter: https://www.bctengineer.com/md/semester_7/wireless_communication/chapter-3 ## Question Explain indoor propagation models (any two). ## Short answer Two models: (1) Partition losses sums attenuation of walls/partitions: PL(d) = PL(d0) + 10n log(d/d0) + Σ PAF. (2) Floor attenuation factor adds floor loss: PL = PL(d0) + 10n_SF log(d/d0) + FAF + Σ PAF. ## Answer Indoor propagation differs from outdoor because distances are short, the transmitter power is low, and walls, floors, furniture and people strongly affect the signal. Indoor channels are classified as **line-of-sight (LOS)** or **obstructed (OBS)**. Two widely used models are described below. #### 1. Partition losses (same floor) model Buildings have many internal partitions (walls, office cubicles, doors). Each partition between transmitter and receiver adds a measured loss. - **Hard partitions** are part of the building structure (brick, concrete walls). - **Soft partitions** are movable and do not reach the ceiling (cubicle walls, cloth office dividers). Path loss is the free-space or reference loss plus the sum of losses of all partitions crossed: ```text PL(d) = PL(d₀) + 10 n log(d/d₀) + Σ PAF (dB) ``` Typical measured partition losses: cloth office partition ≈ 1.4 dB, double plasterboard wall ≈ 3.4 dB, concrete block wall ≈ 13 dB, all-metal wall ≈ 26 dB. #### 2. Partition losses between floors (floor attenuation factor) model Losses between floors depend on the building material, the floor type and the windows. The **floor attenuation factor (FAF)** is the extra loss for each floor between transmitter and receiver. The first floor gives the largest loss; additional floors add less. ```text Floor 3 Rx ───────────── FAF ≈ 6–10 dB Floor 2 ───────────── FAF ≈ 13–16 dB Floor 1 Tx ``` Typical values: about 13 dB for one floor, 18.7 dB for two floors, 24.4 dB for three floors (office building measurements). #### 3. Log-distance path loss model (with variants) Many indoor measurements fit the log-normal form: ```text PL(dB) = PL(d₀) + 10 n log(d/d₀) + X_σ ``` - n = path loss exponent depending on building and surroundings (about 1.6–1.8 in an open LOS corridor, 2 to 3 in offices, up to 4–6 in obstructed paths). - X_σ = zero-mean Gaussian random variable (dB) with standard deviation σ, which models shadowing. The **attenuation factor model** (Seidel) combines both ideas: ```text PL(d) = PL(d₀) + 10 n_SF log(d/d₀) + FAF + Σ PAF ``` where n_SF is the exponent measured on the same floor. #### Use These models are used to plan Wi-Fi access points, femtocells and in-building DAS systems, for example to decide how many access points a three-storey office needs. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which is a soft partition? A. Concrete wall B. Brick wall C. Movable cubicle wall not reaching the ceiling D. Floor slab Answer: C. Soft partitions are movable and do not reach the ceiling; hard partitions are part of the building structure. (Key point: Soft vs hard partitions) 2. In the same-floor partition model, total path loss is: A. Free-space loss minus partition losses B. Reference/log-distance loss plus the sum of losses of partitions crossed C. Only the largest partition loss D. Independent of distance Answer: B. PL(d) = PL(d0) + 10n log(d/d0) + sum of PAF. (Key point: Partition model) 3. How does the floor attenuation factor behave with more floors? A. The first floor adds the largest loss; more floors add less each B. Every floor adds equal loss C. Loss decreases D. Loss is zero beyond one floor Answer: A. Measurements show about 13 dB for one floor, then smaller increments for additional floors. (Key point: Floor attenuation) 4. Which path loss exponent range suits an open LOS corridor? A. 4-6 B. About 1.6-1.8 C. About 8-10 D. Exactly 0 Answer: B. LOS corridors can guide waves giving n about 1.6-1.8, while obstructed paths reach 4-6. (Key point: Indoor exponent) ## Related in Wireless Communication - [Outdoor propagation models (any two)](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Aoutdoor-propagation-models) — Wireless Communication, chapter 3, asked 3× - [Coherence bandwidth/time and indoor propagation factors](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Acoherence-indoor-propagation-factors) — Wireless Communication, chapter 3 - [Basic propagation models and far-field distance](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Apropagation-models-far-field) — Wireless Communication, chapter 3 - [Large vs small scale models; propagation mechanisms](https://www.bctengineer.com/question.md?key=semester_7%2Fwireless_communication%3Alarge-small-scale-propagation) — Wireless Communication, chapter 3 ## Related in other subjects - [VHDL models; full adder structural](https://www.bctengineer.com/question.md?key=semester_6%2Fembedded_system%3Avhdl-models-full-adder-structural) — Embedded System, chapter 9 - [TTL OR gate; propagation delay and power](https://www.bctengineer.com/question.md?key=semester_3%2Fdigital_logic%3Attl-or-propagation-power) — Digital Logic, chapter 10